This invention relates generally to navigation equipment and techniques. This invention relates particularly to rotation sensors.
A rotation sensing system according to the invention comprises a rotation sensor that produces a signal in response to an input rotation about a sensing axis. A servo system is arranged to rotate the rotation sensor at an angle about the sensing axis to null the signal from the rotation sensor such that the rotation sensor is substantially inertially stable. The invention further includes a resolver arranged to measure the angle through which the servo system has rotated the rotation sensor.
The rotation sensor preferably is comprised of a vibratory rotation sensor such as a hemispheric resonator gyroscope that includes a hemispherical resonator that supports standing wave vibrations and a signal pickoff arranged to provide the signal to the servo system.
The rotation sensing system according to the invention preferably further comprises a shaft connected between the resonator and the resolver with the shaft being arranged to rotate with the resonator.
The servo system preferably includes circuitry for processing signals output from the signal pickoff to produce a feedback signal and a servomotor connected to the shaft and arranged to receive the feedback signal and rotate the shaft and hemispheric resonator to null the signal output from the signal pickoff.
The resolver may be mounted on a vehicle and arranged to measure angular displacement between the vehicle and the rotation sensor.